Low aerial burst detonating device

ABSTRACT

A low aerial burst or surface burst detonation shell which is constituted of an accessory to be bolted to a conventional form of bomb. The accessory includes a compartment separated from the interior of the bomb and contains an explosive material which, when detonated, provides a jet stream issuing from the front end of the accessory to propel the bomb in a direction opposite from its original direction. A fuse casing extends through the accessory compartment and into the interior of the main bomb. The fuse is divided into separate portions, each having its own primer device. An arming shaft fitted with an end propeller passes through both fuse compartments. The striking devices in the respective fuse compartments comprise heavy rings threadedly mounted on the shaft and when the latter is rotated by the propeller, the rings are released at the threaded position and placed in an armed condition. As the shell enters the ground, the primer in the forward part of the fuse is detonated by the forward striking ring and the &#39;&#39;&#39;&#39;retro&#39;&#39;&#39;&#39; charge exploded to provide a jet stream which propels the shell backwards. The second compartment of the fuse contains a compression spring which abuts the second or rear striking ring of the fuse. The spring, upon removal of a compressive force exercised by the striking ring during the retro travel drives the ring against the primer and explodes the bomb at a predetermined position above the ground.

United States Patent [72] Inventor William J. Howe Marysville, Calif. (Rte. 1, Alexandria, Pa. 16611) [211 App]. No. 785,460

[221 Filed Dec. 19, 1968 [45] Patented Jan. 5,1971

[54] LOW AERIAL BURS'I DETONATING DEVICE 6 Claims, 5 Drawing Figs.

[52] US. Cl. 102/7.2, 102/70, 102/86 [51] Int. Cl. F42b 25/00 [50] Field of Search 102/27.2, 70, 49.4, 86; 89/15 [56] References Cited UNITED STATES PATENTS 1,235,637 8/1917 Barlow l02/7.2

1,382,750 6/1921 Sprague et al.. 102/7.2X

1,791,716 2/1931 Davis et a1. 102/7.2X

2,316,656 4/1943 Walker 102/7.2X

2,804,823 9/1957 .lablansky l02/49.4

Primary Examiner-Samuel W. Engle AtrorneysHarry A. Herbert, Jr. and Herbert Brown ABSTRACT: A low aerial burst or surface burst detonation shell which is constituted of an accessory to be bolted to a conventional form of bomb. The accessory includes a compartment separated from the interior of the bomb and contains an explosive material which, when detonated, provides a jet stream issuing from the front end of the accessory to propel the bomb in a direction opposite from its original direction. A fuse casing extends through the accessory compartment and into the interior of the main bomb. The fuse is divided into separate portions, each having its own primer device. An arming shaft fitted with an end propeller passes through both fuse compartments. The striking devices in the respective fuse compartments comprise heavy rings threadedly mounted on the shaft and when the latter is rotated by the propeller, the rings are released at the threaded position and placed in an armed condition. As the shell enters the ground, the primer in the forward part of the fuse is detonated by the forward striking ring and the retro" charge exploded to provide a jet stream which propels the shell backwards. The second compartment of the fuse contains a compression spring which abuts the second or rear striking ring of the fuse. The spring, upon removal of a compressive force exercised by the striking ring during the retro travel drives the ring against the primer and explodes the bomb at a predetermined position above the ground.

LOW AERIAL BURST DETONATING DEVICE BACKGROUND OF THE INVENTION Existing fuses are two major designs, one the impact and the other the barometric type. The impact fuse detonates upon contact with a hard surface. However, in a country with marshy features and mobile tactical targets, the effectiveness of the weapon is limited because the explosion causes ineffectual scattering of the shell fragments. On the other hand, a burst, detonated under marshy ground against open or lightly fortified targets and using a delayed action fuse is a poor use of energy for much of the explosion force is absorbed in the ground. The only way to gain the high effectiveness desired in a marshy terrain is to have the explosion occur at a predetermined height above ground. Usually this is accomplished by a special form of fuse, one that is based on barometric pressure. But these fuses are not altogether satisfactory on account of their supersensitivity and, susceptibility to changes in weather and other atmospheric conditions which might produce a wide variation in the height ofthe explosion.

SUMMARY OF THE INVENTION An object of the invention is to provide an improved fuse, and more particularly, an entire bomb containing the fuse which is peculiarly well adapted to marshy terrain targets and is not susceptible to the weakness of the impact or delayed action fuse. This object is attained in brief by dividing the bomb equipped with the improved fuse into two portions with forward and rear charges of explosive material, separate from one another, and causing the bomb to burrow intothe ground at which time the forward charge is exploded to provide a jet action which propels the shell into the air whereupon the second or rear charge is exploded at its most effective height. Inasmuch as the bomb is physically divided into two compartments with the separate charges of explosive material, the improvement lends itself, and in accordance with another aspect of my invention, to employ as the rear portion of the combined device, a conventional bomb with a standard explosive mixture, and replace the ordinary fuse therein by the improved fuse. The forward or retro" portion of the device can be employed as an accessory to be bolted or otherwise secured to the conventional bomb so that the accessory can be attached or not, depending upon its contemplated use. However, in case the accessory is employed as when the combined shell is to be used against marshy terrain, a fuse, improved in accordance with my invention, can be, advantageously used.

Thus, another object of the invention is to provide a bomb or projectile in which the main portion of the explosive material does not explode upon impact with the ground. Instead, it is caused to enter the ground and to return by an underground explosion to a position aboveground before the main explosive portion is detonated.

Another object is to provide a bomb which is constituted of a conventional bomb body fitted with an improved accessory including a special fuse to provide an aboveground explosion after the bomb has impacted the earth.

Another object is to provide a bomb dropped from a plane and constituted of a conventional form of bomb but equipped with an accessory including a special fuse which causes the bomb to burrow into the earth and then be returned by rocket effect to a position above the ground and exploded.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a longitudinal section of a conventional bomb to which is attached the improved explosive accessory and fuse by which the retro" operation is effected and the main charge exploded aboveground;

FIG. 2 is a view looking toward the front end of the structure shown in FIG. 1;

FIG. 3 is a longitudinal section of a structure taken to the right of line A-A in FIG. 1 and showing the right-hand portion of a modified form of the improved fuse extending into the charge of a conventional bomb;

FIG. 4 is a sectional view of the fuse shown in FIG. 3, but in enlarged form, to bring out the details more clearly; while FIG. 5 represents a sectional view taken at the. line 5-5 in FIG. 4 and looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, reference character I designates the cylindrical shell of a standard or conventional bomb made of steel and terminating at its front end in aconically shaped portion having a hemispherical interior. The shell 1 is fitted with the usual guiding vane structure 3 which serves, when the bomb is dropped by a plane, to hold the front end or nose portion of the bomb 2 directed toward the ground. The front end or nose portion of the shell is provided with an aperture 4 which normally would accommodate a standard impact or delayed explosion fuse but in the present case is left open in order to receive an improved fuse which will be described hereinafter. There is bolted to the shell as seen at 5 an improved accessory generally indicated at 6 which is adapted to fit snugly over the front end of the bomb 1 and is held rigidly in position by these bolts so that the two structures, i.e., the shell 1 and the accessory, constitute a single, rigid structure. The front or left-hand end of the accessory 6 terminates in a long, curvilinear portion 7 having'a sharply rounded nose 8 designed to present a streamlined effect. The nose portion 8 is provided with three or more equidistantly spaced openings through which jet streams will flow as explained hereinafter. At the opposite or right-hand end of the accessory 6 there is a relatively thin elongated lip portion 9 having a shape as to fit snugly about the outer forward portion 2 of the bomb. A curvilinear wall 10 of the same substantial thickness throughout its area extends across the accessory. The wall has a reentrant shape to conform closely to that of the central nose portion of the bomb. Four equidistantly spaced bolts 5 are threaded through the lip portion of the accessory to hold the latter firmly in place. The wall 10 is provided with a central opening 11 of the same diameter and coincident with the opening 4 in the nose of the bomb. The purpose of the openings 4 and 11 will be described hereinafter.

DETAILS OF THE IMPROVED FUSE The casing 12 of the fuse is formed as a cylindrical tubing of metal which extends through the entire length of the accessory 6 and for a considerable distance into the envelope 1 of the conventional bomb. The remote end of the fuse casing is closed by a disc 13. A shaft 14 extends through the entire casing 12 and is journaled in one end in the disc 13, and at the other end, is journaled in an opening 15 provided in the nose portion of the accessory. Actually, the shaft is broken at a point market 16 in order to insert a small train of reduction gearing, if desired, so that the shaft could turn many times, perhaps or more revolutions per minute, for every revolution of that portion of the shaft which extends to the right of the reduction gear train. The shaft 14 extends beyond its journal opening and is provided with a propeller 16' the purpose of which will be explained hereinafter. At a position about midway of the length of the casing 12 there is a solid block barrier 17 of metal or plastic material which is secured to the interior surface of the casing. A fairly heavy metal strike ring 18 is positioned to the left of the block 17, this ring being adapted to slide along the shaft unless restrained in a manner now to be described. The shaft 14 at the position where it enters the metal ring is threaded, as indicated at 19 and the interior of the ring 18 is correspondingly threaded so that under normal conditions the ring cannot move from its position abutting the block 17 until the shaft 14 has turned a requisite number of revolutions. This rotational effort would cause the ring to move to the left until the threads become disengaged whereupon the ring could slide freely along the shaft. However, in its initial threaded position, the ring 18 abuts the block. The purpose of this ring is to serve in a manner similar to a firing pin for igniting a primer charge of explosive. At a position intermediate the firing ring !8 and the nose portion 8 of the accessory, there is a tubular mass of substantial thickness and formed of explosive material, as indicated at 20. This material can be molded in solid form and its interior diameter is somewhat greater than the diameter of the shaft, thus leaving a part of the casing 12 free within the ring to provide a number of vent openings 20'.

To the right of the block 17 there is a light coil spring 21 surrounding the shaft and loosely held within the casing. In its normal condition the spring 21 is held under compression by means ofa metal striker ring 22 which is similar to the ring 18. The striker ring is normally adapted to slide along the righthand portion of the shaft 14 but is held against the spring by means of screw threads 23 carried by the shaft 14, which threads engage corresponding threads within the ring. It will be noted that the threads 19 are opposite from the threads which engage the striker ring 22 and hold the latter against the coil 21 under compression. Thus, as the shaft 14 is rotated by means of the propeller l6 and threads within the striker ring 22 are turned, this ring will be moved to the right and eventually become disengaged from the shaft so as to be slidable along the shaft. The spring 21 will continuously bear against the striker ring right up to the point when the latter becomes slidably free of the shaft. A molded annular column of explosive 23' is positioned at the right-hand end of the casing, the column having a diameter greater than the shaft so as to leave a clear space between the latter and the interior surface of the column. A number of vent holes 24 are provided through the casing along this open space.

A so-called retrocharge" 25 constituted of any suitable and well-known explosive material is contained within the confines bounded by the inner surface of the accessory 6 and the exterior surface of the casing 12. However, the main charge of the conventional explosive material contained within the bomb 1, and which is intended to be exploded aboveground, surrounds that portion of the fuse to the right of the separator block 17. It is intended that the retrocharge 25 shall be exploded at a time just preceding the main devastating charge 26 as will be explained hereinafter. I

It is apparent that the elapsed time between the firing of the retrocharge 25 and the main charge 26 can be regulated by the relative positions of the striker rings 18, 22, with respect to their primer charges 20, 23, respectively, and also by controlling the weight and size of the rings as well as the compression strength of the spring 2l. The combined fuse may be made and assembled as a complete entity and in various sizes and lengths for different purposes and is readily insertable into the ordinary fuse opening 4 normally provided in most of the conventional bombs. The latter need to provide, in addition, only four or more threaded bolt holes to receive the attaching bolts of the accessory unit.

OPERATION When the complete bomb with its accessory attached is released from an airplane, a long wire called the arming wire" (not shown) temporarily prevents the propeller from spinning. However, when the wire detaches itself from the bomb at a safe distance from the plane, the bomb travels toward the ground. During this period, the propeller rotates, to cause the shaft 14 to turn at a reduced speed on account of the reduction gears 16. As the threaded portions of the shaft within each of the striker rings 18, 22 move in opposite directions, these rings eventually will become detached from the threads so that they are able freely to slide along the shaft. Thus, the fuse is placed in an armed" condition. However, due to the momentum of the bomb as it travels through the atmosphere and is guided to a large extent by the vane structure 3, the rings I8, 22 merely idle along the shaft; but when the bomb impacts with the ground, and assuming that the ground is marshy or soft, the weight and speed of the loaded shell are sufficient to force the projectile or bomb into the ground. A certain amount of delay is obtained in exploding the primer due to the time taken by the striker ring 18 to move along the shaft and to strikethe body of explosive material. At the same time, the ring 22 at the other end of the casing will be forced against the spring 21 and will cause the spring to be compressed. The body in exploding will give off hot gases which pass through the openings 20- and cause the retrocharge 25 to explode. This charge, upon exploding, gives rise to jet streams passing through the openings 8" and these will propel the bomb upwardly through the openingit had burrowed in the ground. By this time, the spring will have been compressed by the impact and also ,by the acceleration forces in the reverse direction. When the bomb will have reachedthe end of its upward course, the spring will have stored enough energy to cause the striker ring 22 to move along the shaft. The speed attained will be sufficient to impact with and ignite the primer charge. The hot gases given off by the latter pass through the openings 24 and immediately contact the main explosive charge 26 of the bomb 1. The latter is preferably caused to explode about 6 to 10 feet aboveground where it will have great devastating effect. Direct impact on marshy land would have caused a conventional bomb to lose much of its power, throwing up mud and misguiding the metal fragments. However, with the disclosed improvement, the bomb is now caused to explode aboveground where there is nothing to impede the speed of the fragmented shell and consequently provide the maximum lethal effect.

FIG. 3 shows a modified form of the improved fuse, inserted into a conventional form of bomb. This FIG. and the enlargement of the fuse per se shown in FIG. 4 discloses an electrical system by which the delay between theexplosion of the retrocharge 25 and the main bomb charge 26 can be accomplished. In these FIGS., the same parts have been given similar reference characters as in FIG. I. It will be understood that the fuse to the left of the block 17, also the accessory 6 and accompanying parts including the propeller 16 are the same in FIGS. 3 and 4 as were described in connection with FIGS. 1 and 2. The shaft 14 is threaded as indicated at 27 and instead of using a slidable striker ring, in the modified version there is used a metal block 28 (FIG. 5) formed as a cylinder atthe center and two vertically directed wing portions 29. The casing 12 is provided at the top and bottom diametral positions, with two short grooves 30, as seen in FIG. 5, which will permit the wing portions 29 to move a short distance in the longitudinal direction when the shaft 14 is rotated a predetermined number of times. There is a conductor 31 taken from the block member to an electrical delay device 32 of any suitable and well-known type. The outgoing side of the device is connected through a conductor 33 to the primer 23. A conductor 34 is also taken from the primer, preferably at a position diametrically opposite from the conductor 33 to a battery 35. A contact 36 is supported by the battery 35 and this contact is positioned opposite from a contact 37 which is connected to the block 28. Thus, as the shaft is rotated a predetermined number of times, assuming that there is employed the speedreducing gearing mechanism 16, contact is made between the elements 36, 37, due to the movement of the block 28 to the right. However, the primer 23 is not immediately exploded on account of the delay effected at the switch mechanism 32. The timer delay can be so adjusted as to allow the retrocharge 25 of the accessory member 6 (FIG. I) to propel the bomb upwardly due to the jet action referred to hereinbefore until the bomb has reached its ultimate height aboveground. Then the device 32 will allow an electric charge to enter the primer 23 which upon exploding will cause hot gases to pass through the vent openings 24 and thus ignite the explosive material 26 in the main bomb.

From the foregoing it is evident that I have disclosed a bomb which carries a retrocharge so that upon impacting the ground, and preferably so timed that this charge will not explode until the bomb has actually entered the ground. The retrocharge upon exploding will provide powerful jets at the nose end of the accessory which serve to propel the bomb into the air again and cause detonation of the main bomb charge at a predetermined level. When the bomb strikes water, such as a canal, the bomb would emerge at a much sharper angle than upon entering due to the effect of the tins of the vane structure 3. But even so, the necessary delay between explosion of the retrocharge and the main charge can be predetermined knowing the conditions of the place of impact of the bomb.

It is evident that the retro" accessory 6 can readily be applied to a conventional form of bomb and since the fuse 12 would be part of the retro accessory, it would only be a simple matter of inserting the casing 12 with its combined fuse structure into the ordinary fuse port of a conventional bomb. The accessory 6 may be made in different sizes and typical shapes so as to provide a simple changeover from a conventional bomb to one that hasthe retro facility for causing the bomb to first burrow into the ground and then to return aboveground for greater explosive effect.

I claim:

I. An accessory for a conventional bomb including its explosive charge, the rear end of the accessory being adapted to being attached to the front end of the bomb, said accessory comprising: a hollow member of approximately the same .diameter and shape as the bomb at the place of attachment,

said accessory having a rear wall at the place of attachment and curved to a pointed nose at the forward end, said accessory being hollow between said wall and nose portions, a charge of explosive material in the hollow space, a cylindrical fuse supported in the wall portion and extending along the center of the accessory within the charge of explosive material as far as the nose portion, and at the other end extending beyond the wall portion and adapted to be inserted into the interior charge of the bomb, a shaft extending along the longitudinal axis of the fuse and journaled at each end in the casing, said shaft extending through an opening in the nose portion of the accessory, a propeller on the extension of said shaft, a tubular mass of explosive material at each end of the fuse casing to leave an annular space between the shaft and said mass, vent holes extending through the casing in the region of said space, said holes communicating respectively with the explosive charges in the bomb and in the accessory, a detonation device within the casing for each of the masses of explosive material, and means including said shaft and its propeller for arming the detonation devices after the combined bomb and accessory has traveled a predetermined distance.

2. An accessory for a conventional bomb as set forth in claim 1 and in which said means includes a pair of metal rings loosely mounted in the casing and located between said masses of explosive material, one ring being adapted to slide along the shaft in one direction and the other adapted to slide in the opposite direction when the rings are placed in an armed condition in order to strike the respective masses of explosive material.

3. An accessory for a conventional bomb according to claim 2 and in which said shaft is provided with threaded portions, the threads moving in opposite directions, the interior of said rings being threaded to correspond with the threads on the shaft whereby the turning of the shaft causes the rings to become disengaged and rendered slidably free of the shaft and the rings are placed in an armed condition.

4. An accessory for a conventional bomb according to claim 1 and in which said nose portion of the'accessory is provided with at least one opening in the nose portion to which the gases emanated by the explosive material in the accessory gives rise to a jet action which propels the bomb and accessory in a direction reverse to its original direction.

5. A bomb having a cylindrical shape and terminating in a nose portion at one end and provided with guiding vanes at the other end, said bomb being formed of two. compartments A and B separated by a wall, explosive material in each compartment, a fuse extending entirely through compartment A and partway into compartment B through an opening in said wall, the interior of said fuse being divided into two separate sections C and D, a shaft running through said sections to the exterior of the nose portionof the bomb, a pro eller mounted in the exterior portion of said shaft, a primer c arge of SOlld explosive material in each section surrounding said shaft but leaving an annular space therebetween, vent openings in said annular space, a striker ring in each section loosely mounted on said shaft, means in said shaft for holding said striker ring first in an unarmed condition and then, as the propeller rotates, placing each striker ring in an armed condition, at least, one opening in the nose portion of the bomb to allow a jet stream to issue, said striker ring in section C of the fuse being adapted to slide along the shaft and explode the primer charge so as to expel explosion gases through said vent openings upon impact with the ground whereby the explosive material in compartment A is caused to explode and form a jet passing through said nose opening, said jet serving to propel the bomb in the reverse direction to a position aboveground, a spring in compartment B abutting the striker ring and adapted to be placed in compression during the acceleration in said reverse direction, saidspring causing the ring to strike and detonate the solid primer charge in section D of the fuse when the bomb reaches its aboveground position whereby the explosion gases pass through the vent openings in section D to cause the ignition of the explosion material in compartment B.

6. An accessory for a conventional bomb adapted to be secured thereto, said accessory comprising a hollow, cylindrical casing substantially closed at one end to form a nose portion having a wall at the other end which terminates in a hollow body, said body having an end shape as to fit snugly over the bomb, explosive material contained within the casing of the accessory and within the bomb, a fuse for said material, said fuse being constituted of a relatively small cylinder extending through the accessory and through said end wall into the interior of the bomb, a shaft passing along the central axis of the cylinder and carrying a propeller at a position external to said nose portion, a tubular body of explosive material constituting a primer at one end of said cylinder and leaving a space between the shaft and the primer, vent holes through the cylinder within said space, an annular strike ring surrounding the shaft and adapted to detonate said tubular body of explosive material after the bomb has entered the ground, causing gases of explosion to pass through said vent holes whereby the explosive material in the accessory is ignited, said nose portion having openings through which the gases of explosion are forced to provide jet action, a tubular body of explosive material constituting a primer at the other end of said cylinder and leaving a space between the shaft and the primer, vent holes through the cylinder within said last-mentioned space, an annular strike ring adapted to detonate said last-mentioned tubular body of explosive material, a spring surrounding said shaft and abutting said strike ring, said spring when compressed being adapted to furnish the accelerating force for moving said strike ring at a detonating speed along said shaft, the gases from said last-mentioned explosive material passing through said vent holes to ignite the main charge of material in the bomb. 

1. An accessory for a conventional bomb including its explosive charge, the rear end of the accessory being adapted to being attached to the front end of the bomb, saiD accessory comprising: a hollow member of approximately the same diameter and shape as the bomb at the place of attachment, said accessory having a rear wall at the place of attachment and curved to a pointed nose at the forward end, said accessory being hollow between said wall and nose portions, a charge of explosive material in the hollow space, a cylindrical fuse supported in the wall portion and extending along the center of the accessory within the charge of explosive material as far as the nose portion, and at the other end extending beyond the wall portion and adapted to be inserted into the interior charge of the bomb, a shaft extending along the longitudinal axis of the fuse and journaled at each end in the casing, said shaft extending through an opening in the nose portion of the accessory, a propeller on the extension of said shaft, a tubular mass of explosive material at each end of the fuse casing to leave an annular space between the shaft and said mass, vent holes extending through the casing in the region of said space, said holes communicating respectively with the explosive charges in the bomb and in the accessory, a detonation device within the casing for each of the masses of explosive material, and means including said shaft and its propeller for arming the detonation devices after the combined bomb and accessory has traveled a predetermined distance.
 2. An accessory for a conventional bomb as set forth in claim 1 and in which said means includes a pair of metal rings loosely mounted in the casing and located between said masses of explosive material, one ring being adapted to slide along the shaft in one direction and the other adapted to slide in the opposite direction when the rings are placed in an armed condition in order to strike the respective masses of explosive material.
 3. An accessory for a conventional bomb according to claim 2 and in which said shaft is provided with threaded portions, the threads moving in opposite directions, the interior of said rings being threaded to correspond with the threads on the shaft whereby the turning of the shaft causes the rings to become disengaged and rendered slidably free of the shaft and the rings are placed in an armed condition.
 4. An accessory for a conventional bomb according to claim 1 and in which said nose portion of the accessory is provided with at least one opening in the nose portion to which the gases emanated by the explosive material in the accessory gives rise to a jet action which propels the bomb and accessory in a direction reverse to its original direction.
 5. A bomb having a cylindrical shape and terminating in a nose portion at one end and provided with guiding vanes at the other end, said bomb being formed of two compartments A and B separated by a wall, explosive material in each compartment, a fuse extending entirely through compartment A and partway into compartment B through an opening in said wall, the interior of said fuse being divided into two separate sections C and D, a shaft running through said sections to the exterior of the nose portion of the bomb, a propeller mounted in the exterior portion of said shaft, a primer charge of solid explosive material in each section surrounding said shaft but leaving an annular space therebetween, vent openings in said annular space, a striker ring in each section loosely mounted on said shaft, means in said shaft for holding said striker ring first in an unarmed condition and then, as the propeller rotates, placing each striker ring in an armed condition, at least, one opening in the nose portion of the bomb to allow a jet stream to issue, said striker ring in section C of the fuse being adapted to slide along the shaft and explode the primer charge so as to expel explosion gases through said vent openings upon impact with the ground whereby the explosive material in compartment A is caused to explode and form a jet passing through said nose opening, said jet serving to propel the bomb in the reverse direction To a position aboveground, a spring in compartment B abutting the striker ring and adapted to be placed in compression during the acceleration in said reverse direction, said spring causing the ring to strike and detonate the solid primer charge in section D of the fuse when the bomb reaches its aboveground position whereby the explosion gases pass through the vent openings in section D to cause the ignition of the explosion material in compartment B.
 6. An accessory for a conventional bomb adapted to be secured thereto, said accessory comprising a hollow, cylindrical casing substantially closed at one end to form a nose portion having a wall at the other end which terminates in a hollow body, said body having an end shape as to fit snugly over the bomb, explosive material contained within the casing of the accessory and within the bomb, a fuse for said material, said fuse being constituted of a relatively small cylinder extending through the accessory and through said end wall into the interior of the bomb, a shaft passing along the central axis of the cylinder and carrying a propeller at a position external to said nose portion, a tubular body of explosive material constituting a primer at one end of said cylinder and leaving a space between the shaft and the primer, vent holes through the cylinder within said space, an annular strike ring surrounding the shaft and adapted to detonate said tubular body of explosive material after the bomb has entered the ground, causing gases of explosion to pass through said vent holes whereby the explosive material in the accessory is ignited, said nose portion having openings through which the gases of explosion are forced to provide jet action, a tubular body of explosive material constituting a primer at the other end of said cylinder and leaving a space between the shaft and the primer, vent holes through the cylinder within said last-mentioned space, an annular strike ring adapted to detonate said last-mentioned tubular body of explosive material, a spring surrounding said shaft and abutting said strike ring, said spring when compressed being adapted to furnish the accelerating force for moving said strike ring at a detonating speed along said shaft, the gases from said last-mentioned explosive material passing through said vent holes to ignite the main charge of material in the bomb. 